Apple has banned iPhone applications based on Google Voice in a new sign of growing rivalry between the powerful Silicon Valley allies, which have drawn recent regulatory attention for their close ties.

An Apple representative on Monday told Sean Kovacs, an independent programmer whose GV Mobile app was rejected, that some of the small program's functions were too close to what the iPhone already offers.

Google confirmed that its official iPhone app was rejected as well, though it has versions for the BlackBerry and Google's own Android operating system for mobile phones.

Google Voice is a well-regarded service still in testing that allows users to receive calls from multiple phone numbers and place cheap international calls.